• Journal of the Korea institute for structural maintenance and inspection
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• v.2 no.2
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• pp.195-201
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• 1998

The purpose of this study is to evaluate the flexural strengthening effects of RC beams reinforced with carbon fiber sheets (CFS) in variable of strengthening amount and anchorage length of CFS. This study can be summarized as follows ; The CFS shares the tensile stress such as rebar during loading test. Also, as the strengthening amount of CFS is increased, the maximum flexural strength of RC beams reinforced with CFS is increased. Therefore, it is confirmed that the CFS's strengthening method is very effective to improve the flexural strength of RC beams. The maximum flexural strength of RC beams with CFS is determined by bond failure between CFS and concrete surface. So, the evaluation of CFS's strengthening effect can be calculated using the tensile stress of CFS which is peeling. When the anchorage length of CFS is increased, the ductility of RC beams is increased because of delaying the peeling of CFS. But, in case of same anchorage length of CFS, when the strengthening amount of CFS is increased, the ductility is decreased. Therefore, it is considered that the anchorage of CFS in the end zone is necessary.

• Proceedings of the Korea Concrete Institute Conference
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• 1998.04b
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• pp.579-584
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• 1998

The purpose of this study is to evaluate the flexural strengthening effects of RC beams reinforced with carbon fiber sheets (CFS) in variable of strengthening amount and anchorage length of CFS. This study can be summarized as follows. The CFS shares the tensile stress such as rebar during loading test. Also, as the strengthening amount of CFS is increased, the maximum flexural strength of RC beams reinforced with CFS is increased. Therefore, it is confirmed that the CFS's strengthening method is very effective to improve the flexural strength of RC beams. The maximum flexural strength of RC beams with CFS is determined by bond failure between CFS and concrete surface. So, the evaluation of CFS's strengthening effect can be calculated using the tensile stress of CFS which is peeling. When the anchorage length of CFS. But, in case of same anchorage length of CFS, when the strengthening amount of CFA is increased, the ductility is decreased. Therefore, it is considered that the anchorage of CFS in the end zone is necessary.

• Journal of the Korea Concrete Institute
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• v.12 no.1
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• pp.69-77
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• 2000

Recently, many strengthening methods are developed to repair damaged structures, when the original structure is under loading, which causes the difference of initial stresses between original member and bonded material. However, current design method or theory, which mostly depends on ultimately strength design, cannot account the difference of initial stresses between members, and it disregards the reduction of nominal strength. In this study, a new strengthening design theory and the amount of strengthening which can account the difference of initial stresses are developed, and applied to the case when a structure in service is repaired. The results show that the amount of strengthening material depends on the status of damages of structure, and the nominal strength is reduced depending on the degree of damages.

• Proceedings of the Korea Concrete Institute Conference
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• 1999.04a
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• pp.750-755
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• 1999

When the RC frame structures subjected to the seismic load, brittle shear failure of vertical members induces brittle collapse of whole structures. Failure mechanism like this is not desirable. So shear strengthening method to avoid this failure mechanism is needed. Recently, strengthening method using continuous fiber sheet is studied and used widely which have high elastic and high strength characteristics. In this study, RC columns which is strengthened by carbon fiber sheet in the form of tape or whole sheet were tested under the cyclic load. The parameter of this test is the amount of strengthening. As the amount of strengthening increase, strength, ductility and energy capacity increase. The failure mode of test results are shear and bond-split failure.

• Proceedings of the Korea Concrete Institute Conference
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• 2002.10a
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• pp.593-598
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• 2002

Routinely, strength method for the determination of the nominal moment of reinforced concrete beam is assumed to also be suitable for strengthening beams with carbon fiber sheets since typically strengthening beams compromise 98% by volume of reinforced concrete. Flexural capacity of strengthening beam is absolutely dependent upon the type of reinforcement materials, amount of reinforcement, anchoring system, adhesion capacity between reinforcement material and concrete. Therefore, it might be incorrect to use strength method for analysis and design of strengthening beam without considering the differences in the load-deflection curves, mechanism of failure, state of stress distribution, failure strain of the reinforcement. An flexural analysis based on force equilibrium and strain comparability has been developed for strengthening beam. Systematic experimental investigations are compared with analytical results. Then, the adaptation of strength method for strengthening beam have also been discussed.

• Journal of the Korea institute for structural maintenance and inspection
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• v.22 no.4
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• pp.100-107
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• 2018

The objective of this study is to assess the strengthening effects of fiber reinforced polymer(FRP) sheets such as Carbon fiber, Glass fiber, and PET(polyethylene terephthalate) on reinforced concrete flexural members. Variables of theoretical analysis are types of strengthening materials, material properties and amount of strengthening materials. A virtual flexural member without FRP sheets was created as a control specimen to understand the structural behavior of the non-strengthened specimen in terms of elastic and ultimate cross section. In total, 11 specimens including one non-strengthened and ten strengthened specimens were investigated. Various variables such as types of strengthening, strengthening properties, and amount of strengthening were studied to compare the behavior of the control specimen with those of strengthened specimens with regard to moment-curvature relationship. Results of theoretical analysis showed that the moment capacity of strengthened specimens was superior to that of the control specimen. However, the control specimen indicated the best ductility among all the specimens. As the amount of strengthening increased, flexural performance was improved. Furthermore, the results indicated that the ductile effect of members was affected by the ultimate strain of FRP sheets. The strengthening effect on the damaged member was similar to that on the non-damaged one since there was less than 10% difference in terms of flexural strength and ductility. Therefore, even if a damaged member is treated as non-damaged for analysis there is probably no noticeable difference.

• Journal of Industrial Convergence
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• v.19 no.6
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• pp.81-91
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• 2021

This study was conducted to investigate the effect of ankle muscle strengthening exercise using BOSU ball and taping on static and dynamic plantar pressure in patients with hallux valgus. Subjects were 26 men and women in their twenties with hallux valgus, and they were randomly assigned to a taping group (TG; n=13) and an ankle strengthening group (ASG; n=13). Each group received the appropriate intervention over a total of 4 weeks, and static and dynamic plantar pressure were measured before and after the intervention. Independent T-test was performed to examine the difference in the amount of change between groups, and paired-sample T-test was performed to determine whether the difference between the pre-post values within the group was significant. The statistical significance level was set as α=.05. As for the ratio of the total body weight of the foot (Foot), the amount of change in the ASG of the left foot was significantly decreased compared to the TG within the group (p<.05). Significantly increased (p<.05). As for the degree of pronation of the foot (MP/change ratio), the amount of change in the TG of the right foot was significantly decreased compared to the ASG (p<.05), and in the force of the foot, the TG of the left foot was the amount of change within the group compared to the ASG. was significantly increased (p<.05), and in the group-to-group change, the amount of change in TG was significantly different than that of ASG (p<.05). Therefore, it can be considered that ankle strengthening exercise using bosu ball and taping are insufficient to give effective change to patients with hallux valgus.

• Journal of the Korea Concrete Institute
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• v.11 no.3
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• pp.13-21
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• 1999

Recently, many strengthening methods are developed to repair damaged structures, especially, steel plate or carbon fiber sheet bonding methods are widely used. For the bonding methods, the strengthening materials are bonded when the original structure is under loading, with causes the difference of initial stresses between original member and bonded material. However, current design method or theory, which mostly depends on ultimately strength design, cannot account the difference of initial stresses between members, and it disregards the reduction of nominal strength. In this study, a new strengthening design theory and program which can account the difference of initial stresses are developed, and applied to the case when a structure in service is repaired. In order to verify the validity of the theory and the program, a test result is referred and compare with the results and it is showed that the calculated values are almost same as the referred data and finally proved that the program is reliable. The results showed that the amount of strengthening material depends on the status of damages of structure, and the nominal strength is reduced depending on the degree of damages.

• Journal of the Korea Concrete Institute
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• v.11 no.3
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• pp.35-45
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• 1999

Recently, many strengthening methods are developed to repair damaged structures, especially, steel plate or carbon fiber sheet bonding methods are widely used. For the bonding methods, the strengthening materials are bonded when the original structure is under loading, which causes difference of initial stresses between original member and bonded material. However, current design method or theory, which mostly depends on ultimately strength design, cannot account the difference of initial stresses between members, and it disregards the reduction of nominal strength. In this study, a new strengthening design theory and program which can account the difference of initial stresses are developed, and applied to the case when a structure in service is repaired. In order to verify the validity of the theory and the program, a test result is referred and compared with the results and it is showed that the calculated values are almost same as the referred data and finally proved that the program is reliable. The results showed that the amount of strengthening material depends on the status of damages of structure, and the nominal strength is reduced depending on the degree of damages.

• Land and Housing Review
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• v.7 no.4
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• pp.323-328
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• 2016

There are small box opening for inserting of electric lamp box in the slab of apartment. Around this box opening, we normally use the detailing of WWF or plastic ring strengthening to protect cracks induced by shrinkage. The shrinkage amount of slab box around was measured and analysed in order to consider validity of these strengthening methods and to find out economical alternative. Alternative of strengthening methods are normally used strengthening methods in construction companies, which are WWF strengthening, plastic ring strengthening and no strengthening methods. The shrinkage amount was measured using contact guage at the spot of tip attached around the box on slab of small area unit apartment which have small exclusive area below $59m^2$. Measured data shows that there are no big differences between all the 3 strengthening methods and Measure data range is $-264{\mu}{\varepsilon}{\sim}+216{\mu}{\varepsilon}$. Measured shrinkage is on trend slightly increase till 3~5weeks after removal of forms and then decrease. But amount of shrinkage are very low for all the slabs and there are no probabilities of concrete crack by shrinkage.